In the Past, It Was Common for People with Phenylketonuria

Essay

In the past, it was common for people with phenylketonuria (PKU) who were placed on a low-phenylalanine diet after birth to be allowed to return to a normal diet during their teenage years.Although the levels of phenylalanine in their blood were high, their brains were thought to be beyond the stage when they could be harmed.If a woman with PKU becomes pregnant, however, a problem arises.Typically, the fetus is heterozygous but is unable, at early stages of development, to metabolize the high levels of phenylalanine that arrive from the mother's blood.(a) Why is the fetus likely to be heterozygous? (b) What do you think would happen to the fetus during this "maternal PKU" situation? (c) What would be your advice to a woman with PKU who wants to have a child?